1. Field of the Invention
The present invention relates to an inertial sensor for vehicles, and more particularly to an inertial sensor calibration method for vehicles and a device therefor.
2. Description of the Related Art
Considering more comfortable and safer driving, many car manufacturers have started building affordable luxury cars equipped with built-in or attached multi-functional electronic devices, such as adaptive headlights, navigation systems, instant traffic alerts and the like, to implement and assist automatic driving.
Most vehicle electronic devices mainly target at assisting drivers to pay attention to or adjust safe driving functions based on instant traffic condition. Given the adaptive headlight as an example, the high beam, low beam and beam shapes thereof can be switched or adjusted in accordance with a driving or road condition when the vehicle makes a turn, goes uphill or goes downhill. Furthermore, a navigation system indicates current vehicle location and provides driving directions to drivers. Hence, those built-in or attached electronic devices need to obtain the instant dynamic information of vehicles so as to perform the optimized control.
At present the devices normally used to provide dynamic inertial information for vehicles are called inertial sensors, such as accelerometers, gyroscopes and the like. For example, the accelerometers and the gyroscopes serve to detect speed, acceleration and angular velocity of vehicles for truly reflecting conditions of vehicles on the move. The signals sensed from inertial sensors must go through effective computation (i.e. integral computation) to result in useful and correct vehicle moving information. To minimize the error of the computation result, a calibration is usually carried out in collaboration with a GPS navigation system, an electronic compass or a pressure sensor. However, those electronic devices used for calibrating errors generated in computation of inertial sensors are sensitive geographically. For example, satellite signals are lost when the electronic devices pass by high-rise buildings or enter an underground passage, the earth magnetic field strength is relatively weak and the pressure is affected when measured in a tunnel. Hence, the signals originally serving as reference values for calibration either disappear or become worse in terms of correctness so that the error resulting from the integral computation for the sensed signals of the inertial sensors cannot be lowered. Accordingly, the electronic device using sensed signals of inertial sensors as control signals fail to provide most adaptive driver assistance when passing through those geographical zones where signals are gone or attenuated. As far as a navigation system is concerned, the positioning continuity and reliability of the navigation system is both degraded and fails to deliver positioning accuracy when the navigation system passes through an underground passage and fails to smoothly receive satellite signals, and the navigation system may temporarily lose its tracking ability. As far as an adaptive headlight is concerned, the optimized beam projecting angle or beam shape of the headlight may not be available when the headlight goes through the signal-attenuated zones.